In a milking machine, the rubber teat holder forms the contact point between the animal to be milked and the milking machine and thus represents the most difficult part of the entire milking machine. Particular problems thus arise in particular with respect to the head portion of a rubber teat holder. Such a head portion must fulfill at least two main conditions, namely it must on the one hand assure good sealing on the teat and on the other hand it must be able to adjust well to the many different teat sizes, without applying excessive pressure on the teat. A particularly good sealing is needed to avoid entrance of leakage air and to prevent the entire milking cup from falling off the teat in consequence. The problem of falling off is particularly acute if the milking vacuum is adjusted relatively low. However, this low vacuum, according to newer scientific knowledge, has especially important milking-physiological advantages, and clear advantages with respect to the teat treatment, compared with a high milking vacuum.
The mostly sporadic entrance of leakage air into the head portion of the rubber teat means an undesired drop in the vacuum which is needed for the milking operation. The vacuum drop which is caused by the entrance of leakage air, however, cannot simply be balanced by operating the milking machine as a whole with a higher vacuum pump output, because the occurrence of leakage air as such means already an influence on the milk quality, since turbulences are formed in the milk due to the entering leakage air, which damages the milk structure and thus reduces the milk quality.
Moreover, the entrance of leakage air also endangers the health of the udder. More particularly, one of the teats of an udder often already has mastitis. If now air enters at such a diseased teat, the consequence is that, due to the suddenly occurring pressure difference, the milk from the diseased teat reaches through the collecting piece to the healthy teat. As has been shown in experiments, the thus-occurring milk mist has such a speed that the streak canal on the healthy teat has these milk droplets smoothly flow through same.
Practically in conflict with the requirement of good sealing of the head portion on the teat is the second requirement, that the head portion must adjust simultaneously to the many various teat sizes, teat forms, teat positions and teat conditions, without influencing the teat. Special consideration must thus be given to the fact that especially the tissue at the base of the teat is particularly sensitive, because especially in this area end many nerves which are influential in the stimulation of the animal. However, it is just in this area of the base of the teat that the sealing off of the head portion against the teat must occur. Therefore, as a main requirement must be seen the demand that excessive pressure must not be applied at the base of the teat at the level of the annular fold (Furstenbergschen Venenringes), since otherwise this annular fold would close prematurely and thus considerably increase the amount of finish milking. Since the finish milking takes up the largest portion of the necessary routine work per cow, an increased finish-milking amount has an important economic influence. However, yet more important is that poor emptying of the udder has a very negative effect on the course of the lactation curve, namely on the entire product output of the cow. In addition, poorly emptied udders are to a higher degree susceptible to mastitis.
Thus, in conclusion, the rubber teat holder is required to make possible, on the one hand, an optimum sealing and adhesion of the milking cup on the teat and, on the other hand, a quick, gentle, as complete as possible and as automatic as possible emptying of the udder.
Many different rubber teat holders are known, which meet these demands either not at all or only insufficiently. A good capability of adjusting to teats of different sizes is already offered by the large head--flat head--rubber teat holder known from U.S. Pat. No. 2,744,496. In this conventional rubber teat holder, the upper part of the head portion is formed by a flat ring lip with a relatively large outside diameter. This large sealing lip (which is flat or level in its initial position) has the advantage that, when teats of different thickness are introduced into the inlet opening, the lip is bent correspondingly inwardly into the head portion. The sealing lip, which is mounted on its outer edge, can be bent easily inwardly due to its relatively large outside diameter. This causes the inlet opening enclosing the teat to be enlarged, so that even for thicker teats only a small radial pressure is applied to the teat. Such a flat head with a relatively large outside diameter has, however, important disadvantages.
In order for the advantages of the large outside diameter ring lip to be effective during introduction of a teat, the head portion must have a relatively large axial structural height, so that the ring lip can be swung also sufficiently inwardly and downwardly to admit teats of different thickness, without the ring engaging the lower part of the head portion. However, such a large head height has the disadvantage that short teats practically find no hold in the rubber teat holder. Furthermore due to the large diameter of the head portion, reciprocal interferences of the milking cups at the udder can result with very closely positioned teats, which results in a poor udder emptying and mostly in a falling off of the milking cups. These flat-head cups of large diameter have the further disadvantage that the cups fall off due to the leakage air when the milking cup cannot be attached to the teat so that the plane of the flat head extends parallel to the bottom of the udder. This is often the case when, for example, the teats are inclined on the udder or also when the udders are very wide or also in the case of ball or step udders. In these cases the teat cup, due to its weight, tends to position itself so that its longitudinal axis extends vertically. If hereby one side of the upper edge of the head portion comes to rest on the udder bottom, then the danger is that the milking cup may tilt and the ring lip deform at the teat or at the udder bottom, such that leakage air can enter. These problems are particularly great when the udder bottom is still hard and unelastic after calfing or when the teats are particularly thin.
A better capability of adjustment to the above-indicated conditions is shown by a rubber teat holder with an approximately semispherical upper head portion, as it has become known for example from German Pat. No. 936 724. However, this conventional round head portion has the disadvantage that during the introduction of different thickness teats, the ring lip which encloses the inlet opening is swung inwardly. However, during this inward swinging of the ring lip, contrary to the above situations described in connection with the flat head, the inlet opening is not enlarged but further narrowed down, so that the teat is practically clamped in, or pinched in, by a narrowing-down ring. Rubber teat holders with such a round head are therefore mostly only usable for teats having a very specific thickness and form in order to achieve somewhat acceptable milking results. For teats of different thickness, practically in each case different rubber teat holders must be used. This, however, is not acceptable for practical milking operations or from the standpoint of economics.
As a logical consequence, one has therefore tried with the rubber teat holder known from German Pat. No. 1 036 562 to maintain the advantages of a round head portion by constructing the upper sealing lip particularly elastically. Said lip is intended to be so elastic that it rolls in easily during the introduction of different thickness teats, without applying significant pressure to the teat. This, however, requires an extremely difficult material tuning for the sealing lip, because if the material is too hard, a considerable pinching in of the teat occurs, while if the material is too soft the danger exists that the milking cup may fall off from the teat. Even if, however, the material is measured correctly at the start, it has been found in practice that after some use the material characteristics change and the sealing lip mostly becomes too soft, which increases the tendency of the milking cups to fall off from the teat. Such a rubber teat holder is in particular unfavorable also for short teats, since the possibility of the strong rolling in of the sealing lip requires as a whole a relatively large head portion height so that small teats no longer find a hold in the mentioned rubber teat holder. However, even for sufficient length teats, the disadvantage exists that only poor or practically no tissue support against the action of the vacuum exists over a large length of the teat, since the teat hangs nonsupported over a relatively large length in the high head portion and swells accordingly. Aside from the mentioned disadvantages, it has been found in practice that the thin elastic rollable lip is extremely sensitive to material tears, wears very quickly, and is damaged very easily during the rough use on the farm.
Therefore, the basic purpose of the present invention is to further develop the rubber teat holder of the above-mentioned type according to German Pat. No. 1 036 502, which rubber teat holder has a round head portion, so that its capability of adjusting to different thickness teats is improved.
This purpose is inventively attained (1) by the first spring joint being formed by the wall portion which lies approximately at the level of the maximum outside diameter of the head portion; (2) by the wall portion in the lower tapering head part, at the level of a cross plane perpendicular to the longitudinal axis, acting as a second spring joint in response to axial pressure on the inlet opening of the teat holder, the wall portion extending between the first and second spring joints being pivotable about the second spring joint during enlargement of the outside diameter of the head portion, like a lever of approximately constant length; (3) by the connecting line (viewed in central cross section) between the first and second spring joints defining an angle of less than or equal to 45.degree. with the cross plane; and (4) by the mean diameter of the tapering head part being smaller at the level of the second spring joint than the largest inside diameter of the milking cup sleeve.
This makes possible a particularly small round head portion, which head portion permits a superb capability of adjustment to extremely differing teat positions and udder forms, without causing the danger of falling off or entrance of leakage air.
If one makes the angle between the first and second spring joint larger than 45.degree., then the lower part of the head portion becomes so stiff, being practically a cone-shaped shell, that axial pressure on the head portion can no longer effect an active enlargement of the outside diameter of the head portion. Thus, pivoting of the lower wall portion of the head portion could no longer take place. In such a configuration, a small enlargement of the outside diameter of the holder could be made possible only by radial pressure on the upper sealing lip during introduction of the teat past the sealing lip. However, this radial pressure acts back fully onto the teat, so that in such a configuration a pressure relief of the teat can no longer take place. In contrast, the inventive construction, wherein the angle between the first and second spring joints is chosen smaller or at most equal to 45.degree. and preferably is between 45.degree. and 20.degree., achieves enlargement of the maximum outside diameter of the head portion in response to axial pressure acting through the two spring joints and the therebetween-lying relatively longitudinal-pressure-resistant wall portion, due to outward pivoting of said wall portion. The smaller the mentioned angle, the easier is the outward pivoting of such wall portion in response to axial pressure on the head portion. Radial pressure on the teat is thus relieved in the present invention.
Such radial pressure relief is achieved by the present invention in particular also toward the end of milking. The teat usually becomes softer as the milking time continues. This usually reduces the sealing action which exists at the beginning between the teat and the suction sleeve, so that the vacuum in the head cavity of the rubber teat holder increases more and more. Due to the resulting change in pressure difference between the outside atmosphere and the pressure inside of the head cavity, the relatively soft upper ring lip is pressed axially downwardly. Due to the pressure difference, in the case of a flat-head rubber teat holder, said operation results in an enlargement of the opening and thus entrance of leakage air. In contrast, in the case of a round-head rubber the teat inlet opening is further narrowed down, so that in the case of the up-to-now common round-head rubber teat holders a further additional constriction of the teat actually results. However, in the inventive rubber teat holder further pressure relief is achieved due to the pivoting of the lower head part outwardly. The degree of the desired pressure relief can be selected easily by selecting the length of the distance between the first and the second spring joint and by selecting the angle between the connecting line between said spring joints and a cross plane perpendicular to the longitudinal axis of the rubber teat holder. The larger the distance is between the first and second spring joints, the larger is (under otherwise the same conditions) the relieving action. The flatter the mentioned angle, the easier is the reaction of the system to a changing pressure difference between the outside atmosphere and the inside pressure in the head cavity, or to an axial pressure on the upper end of the head portion of the rubber teat holder. A relief is thus achieved according to the invention especially due to its geometric and structural characteristics.
The rubber teat holder of the invention can be constructed both as a rubber teat holder for a two-chamber cup and also for a one-chamber cup. Usually in the case of a rubber teat holder for a one-chamber cup, one does not need a suction sleeve connected to the head portion, since in this case the inner wall of the suction sleeve is usually replaced with the inner side of the cup sleeve. In a one-chamber cup it is advantageously true that the mean diameter of the tapering part of the head portion is smaller at the height of the second spring joint than 1.5 times the inner suction sleeve diameter. The inside diameter of the suction sleeve is hereby supposed to be determined by measuring at a distance of the maximum head diameter from the upper end of the head portion. This condition results from the general condition that the mean diameter of the tapering part of the head portion is smaller at the height of the second spring joint than the maximum inside diameter of the cup sleeve, if one for example assumes that in a normal milking cup sleeve the maximum inside height measurement is approximately 39 mm. and the suction sleeve has approximately an inside diameter of 26 mm.
The inventive rubber teat holder both for a one-chamber and also for a two-chamber cup has the advantage that the advantages of a round head are maintained, so that the danger of the occurrence of leakage air can be avoided even in the case of the most unfavorable teat positions and udder forms. This advantage is achieved even more since the invention permits manufacture of a round head portion with a specially small maximum diameter. However, it is particularly advantageous that, in spite of the utilization of the advantages of a round head, the capability of adjusting to teats of different thickness and different length is substantially improved. Due to the fact that the possibility is created that the maximum outside diameter of the head portion can increase when teats with different thickness are introduced into the head portion, it is achieved that also in the case of thicker teats practically no greater pressure is applied onto the teat than in the case of thinner teats. This is extremely important for the willingness of the animal to give the milk at all. These advantages are achieved even though the inventive head portion can be constructed especially small and the head height can be constructed very low, so that the rubber teat holder is suitable also for extremely short teats.
These advantages are achieved in a special degree when the second spring joint is arranged at the transition of the tapering part of the head portion into a nozzle (a shortened suction sleeve).
In this last case, the holding edge is advantageously connected directly below the second spring joint to the nozzle. This keeps as short as possible the length of teat engaging the nozzle, wherein no massaging movement is applied by the nozzle to the teat, in that the nozzle is substantially reinforced and practically rigid.
The head portion is advantageously further developed by making the angle (in central cross section) between the first connecting line (between the first and the second spring joint) on the one hand and a second connecting line (between the inside edge of the inlet opening and the first spring joint) on the other hand smaller or equal to 90.degree.. If this angle is exceeded, then the disadvantage results on the one hand that the height of the head portion becomes larger than desired, and on the other hand that the wall of the head portion increasingly proves to be practically stiff with respect to an axially acting force and it forms a cone-shaped surface making an acute angle to the longitudinal axis. For this reason, the angle between the second connecting line, and a cross plane perpendicular to the longitudinal axis, is also preferably chosen smaller than or equal to 45.degree.. In a particularly advantageous embodiment, the radius of curvature of the inside wall at the transition of the tapering part of the head portion into the suction sleeve, or nozzle, is between 1/5 and 1/2 of the diameter of the nozzle. This contributes to keeping the height of the head portion as small as possible and supports the teat at as small as possible a distance from the teat inlet opening. According to a preferred exemplary embodiment, the radius of curvature lies between 5 and 10 mm.
To improve the sealing off of the sealing lip of the head portion, one or several sealing ribs are provided concentrically to the inlet opening around same on the outside of the head portion.
Furthermore, when the holding edge for gripping over the milking cup sleeve is constructed (as seen in central cross section) angularly with two legs, of which the first leg has the free end and rests against the outside of the milking cup sleeve, it is advantageous to make the second leg so flexible that the head portion can move axially with respect to the milking cup sleeve, in response to a pressure difference which occurs between the outside and the space between milking cup sleeve and suction sleeve and acts on the second leg. This contributes considerably to the stimulation of the animal, since at every pulsation cycle the milking cup sleeve is moved longitudinally relative to the teat. This up-down movement is particularly advantageous, when in the case of four teats each two milking cups are switched in push-pull, so that a reciprocal rocking movement is obtained practically on the two pairs of teats, which rocking movement simulates the movement carried out by hand during manual milking.
To avoid a breaking through of the holding edge of the rubber teat holder due to hitting of an object, and merely due to the up and down movement of the milking cup sleeve during the milking cycle, the inside diameter of the holding edge is preferably of thickness increasing from the free end of the holding edge, so that the holding edge part, which in mounted condition grips over the uppermost edge of the milking cup sleeve, has in nonmounted condition an inside diameter larger than or equal to the outside diameter of the milking cup sleeve edge. In addition, it is advantageous to reinforce the holding edge part which grips over the uppermost milking cup sleeve edge.